This article examines external support for school leaders, and focuses on the relationship between head teachers and other professionals who play the role of their 'critical friends'. Most existing research in this area concentrates upon the activity of the critical friend without reference to the role partner, thereby losing the dynamic in the relationship and the contribution of the head teacher to its effectiveness. A small-scale study of head teachers and their local authority advisers acting as critical friends provides the empirical basis for insights into the nature and challenges of the relationship and points the way to further research in this area of increasing policy significance in England.